Casting



Patented Aug. 6, 1940 UNITED STATES PATENT OFFICE CASTING ApplicationApril 18, 1938, Serial No. 262,630

1 Claim.

The present invention relates to casting of the kind in which the metalis put into the mold under the combined influence of plus and minus airpressure and it relates more particularly to a method or mode and toapparatus for practicing the method or mode.

One object of the present invention is to minimize the introduction ofair and gases into the mold in advance of the metal.

Another object of the invention is to improve the quality and characterof the'castings.

Another object of the invention is to provide apparatus by means ofwhich the method or mode can be economically and successfully praclliticed.

Other objects of the invention will appear from the followingdescription at the end of which the invention will be claimed.

Generally stated, the invention consists in raising the metal from aclosed reservoir to a predetermined level in respect to the entrance tothe mold by subjecting the molten metal to the diiference betweenatmospheric pressure and a vacuum or partial vacuum in consonance with 5its specific gravity, thereby displacing from the path of the metal airand gases, and then introdncing the metal from that level into the moldby superatmospheric pressure.

The invention also consists in a reservoir 30 adapted to contain moltenmetal and open to the atmosphere, a closed vessel arranged in thereservoir and in the molten metal therein and provided with a dip standpipe and with an inwardly opening check valve, a vacuum chamber 35adapted to be connected with the open end of the stand pipe through theinstrumentality of a closed mold, and valved means for connecting theinterior of the vessel above the dip end of the pipe, with (a) theatmosphere to establish sub- 40 stantially the same liquid level in thereservoir and dip pipe and vessel; and, after exhausting the stand pipethrough the mold and permitting the level to rise in the stand pipe to apoint predetermined by atmospheric pressure and vacuum 45 pressure andby the specific gravity of the molten liquid, (b) with a source of airunder pressure to force the metal into the mold.

The invention also comprises the improvements to be presently describedand finally 5o claimed.

In the following description reference will be made to the accompanyingdrawing forming part hereof and in which, 4

The single figure is a view principally in cen- 55 tral sectionillustrating the condition just prior to forcing the molten metal fromthe stand pipe into the mold and in which the molten metal stands atthe. level indicated at A.

Referring to the drawing, I is a reservoir or melting pot adapted tocontain molten metal 5 and open to the atmosphere. 2 is a closed vesselarranged in the reservoir I and dipping into the molten metal containedin the reservoir. The vessel 2 is provided with an inwardly openingcheck valve 3 and with a dip stand pipe 4. The 0 dip stand pipe 4 isprovided with a nozzle 5 adapted to enter the sprue hole 6 in the moldand with a gasket I. The halves I! and 9 of the mold are suitablysecured together by means not shown because too well understood torequire 15 illustration or description and if desired a packing II) maybe provided between them. The mold as a whole may be arranged to slidehorizontally on the base I9 to bring the sprue-hole B into and out ofengagement with the nozzle 0 5; or the lower half 9 may be immovablymounted on the base I9, the upper half 8 being removable for taking thecasting out of the mold and admitting air to the stand pipe 4 throughthe sprue hole 6 and the nozzle I. One of the mold halves, 9 in thepresent instance, is provided with a vacuum chamber II connected withthe mold cavity III by a channel I2 of cross section appropriate topermit the passage of air and to prevent the passage of molten metal.The chamber II is connected by a connection I3 to vacuum or to a sourceof minus air pressure such as an exhaust pump. The connection I3 may bea flexible rubber tube if the mold as a whole is movable.

I4 is a pipe communicating with the interior of the chamber I above thelower end I5 of the dip pipe. This pipe I4 by means of the valve I6 maybe connected to atmosphere as at I 'I or to a source of air underpressure as at I8. The source of air under pressure is not shown or de-40 scribed because it is too well understood to require eitherillustration or description.

level of the molten metal will be the same in reservoir I, vessel 2 anddip pipe 4. The exhaust pipe connected to I3 is operating and drawingair from the atmosphere.

The mold is now closed and, if movable, slid into connection with nozzle5. The air in the mold cavity and in the upper end of dip pipe 4 isimmediately exhausted through connection l3, causing the metal to risein pipe 4 to the level indicated at A in the drawing, determined by thedifferential of pressure and the specific gravity of the molten metal.Then the valve "5 is turned to disconnect pipe [4 from the atmosphere(via l1) and connect it to high pressure air via l8. This pressureapplied to the interior of vessel 2 closes check valve 3 and forces themolten metal through dip pipe 4 and nozzle ,5 into the mold cavity 20,unobstructed by the presence of air or gases which have been exhaustedas described above.

The valve I6 is then turned to its original position, shutting ofi thehigh pressure air and connecting pipe l4 to the atmosphere, the mold, ifmovable, is slid away from nozzle 5, is opened and the casting removed;the molten metal in pipe 4 falls to the original level and the cycle ofoperations is repeated.

It will be obvious to those skilled in the art to which the inventionrelates that modification may be made in details of construction andarrangement without departing from the spirit or the invention which isnot limited in respect to such matters or otherwise than as the priorart and the appended claim may require.

I claim:

Method of casting in a mold located a substantial distance above apressure chamber and connected to said pressure chamber by a pipeleading from below the metal level in the pressure chamber to the sprueof the mold, which method consists in applying atmospheric pressure tothe molten metal in the pressure chamber, closing and completelyevacuating the mold to raise the metal in said pipe to a point justbelow the sprue, continuing these conditions until the molten metal inthe pipe comes to rest, closing the connection from the pressure chamberto the atmosphere and connecting said chamber with a source ofsuperatmospheric pressure to force the molten metal through the pipeinto the mold, maintaining said pressure conditions until the moltenmetal in the mold has set, then cutting off the flow of superatmosphericpressure to the pressure chamber and again subjecting the pressurechamber to atmospheric pressure to draw the molten metal metal down saidpipe and below the sprue, and opening the mold to remove the casting.

CHARLES D. GALIOWAY.

